The applicant of the present invention has prior hereto developed a flywheel assembly and has filed Japanese patent application No. 60-44298 and corresponding copending U.S. patent application Ser. No. 836,365, now U.S. Pat. No. 4,751,993, dated June 21, 1988, and West Germany patent application No. P 36 07 3989-13 thereon.
In prior development, as shown in FIG. 4, a first flywheel 104 fastened to an engine crank shaft 100 and engaged and disengaged by a clutch disc 102 a second flywheel 106 installed concentrically with the first flywheel and set to a specified mass, a damper mechanism 108 resiliently coupling the both flywheels, and a friction damping mechanism 105 which transmits an output from second flywheel 106 to a spline hub 103 of the clutch disc 102 and damps its vibration only when said clutch disc 102 contacts with the first flywheel 104.
As shown in FIG. 5, the first flywheel 104 and second flywheel 106 absorb an vibration which transmits from the crank shaft 100 with an power, and the frictional damping mechanism 105 damps the vibration.
However, hysteresis torque Thd generates between the hub flange 103 of the clutch disc 102 and the side plate 109 (FIG. 4). In some cases, the hysteresis torque Thd have an undesirable influence upon damping characteristics.
Further, a damping function of the frictional damping mechanism 106 for the second flywheel 106 comes to a stop, during clutch releasing operation while the clutch disc 102 is disconnected from the first flywheel 104. There is a possibility that the second flywheel will have a resonance phenomenon depending upon the frequency of the input vibration.